This paper introduces an efficient algorithm for finding the dominant generalized eigenvectors of a pair of symmetric matrices. Combining tools from approximation theory and convex optimization, we develop a simple scalable algorithm with strong theoretical performance guarantees. More precisely, the algorithm retains the simplicity of the well-known power method but enjoys the asymptotic iteration complexity of the powerful Lanczos method. Unlike these classic techniques, our algorithm is designed to decompose the overall problem into a series of subproblems that only need to be solved approximately. The combination of good initializations, fast iterative solvers, and appropriate error control in solving the subproblems lead to a linear running time in the input sizes compared to the superlinear time for the traditional methods. The improved running time immediately offers acceleration for several applications. As an example, we demonstrate how the proposed algorithm can be used to accelerate canonical correlation analysis, which is a fundamental statistical tool for learning of a low-dimensional representation of high-dimensional objects. Numerical experiments on real-world data sets confirm that our approach yields significant improvements over the current state-of-the-art.
Stochastic optimization for PCAOver the past few years, the challenges of dealing with huge data sets have inspired the development of novel optimization algorithms for empirical risk minimization (see, e.g., [3] and references therein). Leveraging ideas from stochastic optimization, several scalable algorithms have also been proposed for different eigenvalue problems [8,14,21,26,27]. These algorithms try to combine the low iteration cost of the stochastic methods and the high accuracy of the standard deterministic techniques. Notably, borrowing the idea of variance reduction [15], the author in [26] studied a variant of Oja's algorithm [19], giving the first linearly convergent algorithm for stochastic PCA. The authors of [8] improved the result further by using the well-known shift-and-invert technique from numerical linear algebra [11,22]. Inspired by the momentum method as known as the Heavy ball method in the optimization literature [20], an accelerated stochastic PCA was proposed in [21].